People mix these two up constantly, and on a Biscay crossing the confusion can be dangerous, because a drogue and a sea anchor are deployed at opposite ends of the boat and solve opposite problems. I carried the wrong assumptions for a long time myself. It took a delivery skipper sketching the difference on a paper chart, somewhere off the Vendee coast with a low filling in behind us, before it finally landed.
So before the buying advice, the distinction, because it is the whole decision.
Two devices, two ends, two jobs
A sea anchor is a large parachute streamed from the bow on a long rode. It stops the boat almost dead in the water, holding the bow into the seas and limiting your drift to under a knot. That last figure is the reason to carry one: when sea room is short and you cannot afford to be blown towards a lee shore, the sea anchor pins you in place. The trade is that it loads the boat heavily, snubs hard against each wave, and leaves you lying to the seas with no steerage at all.
A drogue is a smaller device, or a string of small cones, towed from the stern. It does not stop the boat. It slows you to a controlled 3 to 6 knots running before the weather, takes the surf out of the descent down each wave face, and keeps the stern square to the breaking crests so you do not broach. You still make way, downwind, which off the open Atlantic is usually fine because you have the room.
The short version: sea anchor to stop and hold position, drogue to keep moving safely downwind. For a Biscay crossing where the danger is a depression catching you in deep water with plenty of room to leeward, the drogue is the tool I reach for. A boat trapped on the Atlantic coast with a lee shore close astern is the rarer case where the sea anchor earns its keep. Which scenario you face depends on your route, and the biscay passage planning write-up lays out the corner-to-corner versus coast-hugging options that decide it.
Why I went for a series drogue
Not all drogues are equal. A single cone or a small chute does the job but loads up unevenly and can stall or snatch. The Jordan Series Drogue, designed by engineer Donald Jordan after studying real capsizes, is a long line carrying scores of small fabric cones, with a weight at the bitter end. The cones share the load, so there is always grip in the water even as the boat surges, and the whole rig sets itself.
The engineering backs it up. A computer study showed that two seconds after a wave strike, a series drogue develops around 40 percent more load than an equivalent single cone or chute, which is exactly when you want the brake to bite hardest. Cruisers who have streamed one in survival conditions report the boat riding stern-on with little yaw, the threat defused, the crew able to go below and wait it out. That last part matters: a device you can set and then leave is worth far more than one that needs a body in the cockpit through the worst of it.
The number of cones scales with displacement. A 6,600 lb boat wants around 130 cones; a 12,000 lb boat around 140; an 18,000 lb boat around 150; up to 160 cones for a 33,000 lb vessel. Get the count right for your loaded weight, not the brochure displacement, because a cruising boat provisioned for an ocean leg is heavier than the spec sheet.
What it costs to carry one
A ready-made series drogue is not a small purchase, but it is not yacht-budget money either. Commercial sets run roughly from around 1,300 US dollars for a small-boat 130-cone drogue up to about 1,700 for the largest 160-cone version, before you add the bridle, the chainplate attachments and the stern weight. In sterling and euros that lands somewhere in the four-figure bracket once rigged, which against the cost of a Biscay rescue, or a boat, is cheap insurance.
You can save by sewing your own from a kit, and plenty of voyagers do, but the cones are fiddly and the splicing has to be right because the loads are real. If you are not confident, buy it made. The attachment points are the part not to skimp on: the drogue can load the stern with several tonnes in a breaking sea, so the chainplates or strong points need to be through-bolted to proper backing, not screwed to a toerail.
Deploying it without drama
The mistake is leaving the first practice for the storm. Stream the drogue once in moderate conditions, in deep water, so you know how the bridle sets and how the boat lies. The Jordan rig goes out over the stern with the weight first, and once it is all out the boat settles to a slow, elastic, stern-to motion. You feed it out in stages rather than dumping the whole bag, because a tangle of cones going over the transom in a real sea is a nightmare to clear.
Mind the cockpit when you stream it. The loaded line tries to saw across the stern, so lead the bridle through dedicated fairleads or over a smooth quarter, never round a sharp toerail edge that will chafe through it in hours. Close the companionway and secure everything below before you deploy, because once the drogue is set you are committed to riding it out and you do not want loose gear flying around the cabin while you wait.
Recovery is the hard part. You cannot simply winch in a fully loaded series drogue, so you wait for the weather to ease and bring it in hand over hand as the load drops, or motor up to it gently. Plan stowage too: the line and cones bag up large and heavy, and you want them accessible from the cockpit, not buried under the spare anchor.
A drogue is part of a heavy-weather kit, not the whole of it. It sits alongside the dewatering plan in the bilge pump dewatering piece, the beacon in the epirb or plb cruising france guide, and a crew that can work the foredeck shorthanded, which the short handed deck gear write-up covers.
What a sea anchor needs if you do carry one
If your sailing genuinely puts a lee shore close astern, the Atlantic coast in an onshore gale being the classic case, then the sea anchor is the right tool and it has its own kit demands. The rode has to be long and elastic, often three boat lengths or more of nylon, so the snubbing load on each wave does not shock-load the bow fittings to destruction. A swivel and chafe protection where the rode passes through the bow roller are not optional, because a sea anchor left out for hours saws through an unprotected line.
The motion lying to a sea anchor is violent compared with the drogue's elastic stern-to ride, and the boat hunts from side to side as the bow falls off and snatches back. Some boats lie better with a riding sail aft to steady them. None of this is a reason not to carry one where the geography demands it, but it is a reason to understand that the sea anchor is the more demanding device to deploy and to live with. For most Biscay crossings, with open water to leeward, you will never need it.
My honest take
If you cruise the Atlantic coast and intend to cross Biscay, carry a series drogue and learn it. The single best protection against a Biscay gale is still not leaving in the wrong weather window, and a properly studied forecast keeps you out of the situation entirely far more often than the drogue ever gets wet. But the bay catches people who did everything right and got an unforecast low anyway, and on that one night the drogue streaming quietly off the stern is the difference between a frightening passage and a tragic one.
Buy the sea anchor only if your sailing puts you regularly near a lee shore with limited room. For the open crossing, the drogue is the kit I would never set off without.
